Pulsation-preventing mechanism for centrifugal compressors.



- C. A. SCHELLENS. PULSATION PREVENTING MECHANISM FOR CENTRIFUGAL COMPRESSORS. APPLICATION FILED 1AN.26, I918.

1,281,217. Patented Oct. 8, 1918.

I I OVeOtOI', Christopher- J I. Schel lens,

e MM His aqttol-ney the nature of an emergency governor ED STATES PATENT OFFICE;

CHRISTOPHER A. SCHELLENS,

0F CLIFTON, MASSACHUSETTS, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

Specification of Letters'latent- Patented Oct. 8, 1918.

Application filed January 26, 1918. Serial No. 213,850.

To all whom it may concern:

Be it known that I, CHRISTOPHER A. SonnLLENs, a citizen of the United States, residing at Clifton, in the county of Essex, State of Massachusetts, have invented certain new and useful Improvements in Pulsation-Preventing Mechanism for Centrifugal Compressors, of which the following is a specification.

The present invention relates to centrifugal compressors such asare used for compressing air or other gases, and particularly to mechanism for preventing the occurrence of pulsations which are likely to occur under certain conditions of operation.

For Certain classes of work centrifugal compressors are equipped withconstant volume governors which operate to keep a constant volume of air per unit of time passing through the machine. One such known type of constant volume governor comprises a pivoted beam which is connected to a regulator for controlling the motor which drives the compressor and is actuated by a float located in the intake of the compressor and acted upon by the air or other gases entering the compressor. Such a set is also provided with a speed governor which acts i3 an takes control when the speed reaches a predetermined high point.

The object of my invention is to provide an improved pulsation stopping apparatus which is combined with a constant volume governor mechanism as described above, or of other suitable type, and which will operate effectively to prevent pulsations under all conditions of operation.

As is Well known, pulsations in a centrifugal compressor may be prevented by throttling the intake of the machine, by permitting fluid to escape or be wasted from the discharge side of the machine, or both. In thecase of wasting fluid from the discharge side of a machine, the discharge may be to atmosphere or it may be'led back to the inlet side of the compressor. A valve mechanism for this purpose located in either the inlet of the compressor, in a by-pass or waste conduit leading from the discharge side of the compressor, or both, may be termed a pulsation preventing valve mechanism and my improved apparatus may be used in connection with any such arrangement.

It is now known, as set forth in my prior application, Serial No. 146,112, filed February 2, 1917, that the pulsation point in any particular compressor depends on the volume' flowing through the compressor and the pressure on the discharge side of the machine, and particularly on the load-coefficient of the compressor,- which is the ratio of volume to square root of pressure,. If this coefficient is relatively large the machine will operate smoothly; but if it decreases below a certain value then pulsations will occur.

More particularly the object of my invention is to provide improved apparatus which will actuate the pulsation preventing Valvemechanism at all times in accordance with the volume flowing through the machine and the discharge pressure, and which may be adjusted to actuate it substantially in accordance with the load coefiicient of the machine.

For a consideration of what I believe to be novel and my invention, attention isd irected to the accompanying .specification and the claims appended thereto; 4

In the drawing, the figure is a diagrammatic perspective view of an apparatus embodying my invention.

Referring to the drawing, 5 indicates a driving motor, for example, an elastic fluid turbine, and 6 a centrifugal compressor driven thereby and having an inlet conduit 7 and a discharge conduit 8. A regulating meohanism 9 is provided for the motor 5, a well known type of valve mechanism for controlling admission of elastic fluid to a turbine being same being provided with a fluid actuated motor 10 which is controlled by pilot valve 11,the stem of whichis actuated by a lever 12. The connections of the lever 12 to the pilot valve and motor 10 embody a usual form of beam 13 to set the governor mechanism for different volumes, and 18 indicates a float located in the inlet 7 of the compressor and shown in the present instance, the

having a stem 19 connected to the governor beam 13 in the usual manner. The'beam 13 'is provided with a counterweight 20, the

purpose of which is to balance the same. Rigidly connected-to shaft 14 is an arm 21 connected by a link 22 to a bell crank lever 23 pivoted at its elbow on a fixed support 24. The bell crank lever23 is connected by a link 25 to one end of a floating lever 26 which is connected by a rod 27 to lever 12. The other end of floating lever 26 isconnected by a link 28 to a governor lever 29 actuated by a speed governor 30.

The mechanism so far described is that of a known form of constant volume governor, the operation of which is well understood and which may be explained briefly as follows:

The weight 17 is set alon the beam 13 for the desired volume of flow and with this volume being delivered by the compressor the float 18 assumes a definite position in the inlet 7 of the compressor and maintains the valve mechanism 9 in a specified position. If now for any reason the volume of fluid flowing through the compressor decreases then the float 18 lowers a little. This results in turning the beam 13 on its pivot,

which in turn actuates the valve mechanism 9 through the arm 21, link 22, bell crank lever 23, link 25, floating lever 26, rod 27 and lever 12, to cause it to open somewhat to admit'more elastic fluid to the turbine thereby causing the speed to increase, and hence increasing the amount of fluid flowing through the machine. In case the amount of fluid flowing through the machine increases slightly, a similar operation takes place, except that it is in the opposite direction. The speed governor 30 is set so that for ordinary speeds it is ineffective, the mechanism being entirely under the control of the volume governor. In case of excess speed, however, the governor 30 takes the control away from the volume governor and prevents the speed from increasing above a certain value, as is well understood.

Connecting the discharge conduit 8 of the compressor to the inlet 7 thereof at a point in advance of the volume governor float I8- is a by-pass conduit 31 in which is located a pulsation preventing valve 32 provided with an actuating arm 33. Connected to arm 33 is one end of a link 34, the other end of which is provided with a pin which slides in a cam slot 35 formed in a cam plate 36. The cam plate 36 has a T-shaped head 37 which slides in a fixed guide 38, and it is connected by a projection 39, arm 40, shaft 41. arm 42, and link 43 tothe lever 15. The

shaft 41 is suit-ab] y journaled in fixed bracket arms 44. Connected to lever 15 at the end opposite to that in which shaft 14 is pivoted is a pressure responsive device 45, which is subject to the pressure on the discharge side of the compressor througha pipe 46. The pressure responsive device 45 in the present instance is shown in the form of a cylinder and piston, the stem 47 of the piston being connected to the lever 15. 48 is a suitable counterweight which is provided for the lever 15. Associated with the bell crank lever 23 are stops 49 and' 50 which serve to limit the movement of lever 23.

It will be seen that the position of the pivot point B of beam 13 depends on the pressure on the pressure responsive device 45 2'. e., the discharge pressure of the compressor and the pressure being exerted on the float 18 by the incoming fluid. An increase of the pressure on device45, which means an increase in the delivery pressure, acts to raise the piston therein and to lower the pivot point B, and a decrease in the quantity of fluid entering the compressor decreases the float force and also acts to lower .the pivot point B. On the other hand, a

decrease in the delivery pressure Or an increase in the quantity of fluid entering the compressor acts to raise the pivot point B. Lowering the pivot point B moves the link 43, arm 42, shaft 41, and arm 40 in a direction to pull the cam plate 36 downward, and

raising such point moves them in a direction to move the cam plate 36 upward. The cam slot 35 in cam plate 36 has alower straight portion followed by a. curved portion, and so long as the pin on the end of link 34'remains in the straight portion, a vertical movement of the cam plate 36 in either direction does not afl'ect the pulsation preventing valve 32. When the cam plate 36 is moved downward, however, until such pin enters the curved portion of the cam slot 35, then the valve 32 will be gradually opened. This occurs when the relation between volume and delivery pressure becomes such that pulsations are likely to occur.

When the float 18 lowers an amount which represents a speed equal to or greater than that at which it is desired to run the ma.- chine, the arm of hell crank lever 23 strikes stop 50 and prevents further operation of the regulating mechanism 9 by the volume governor. At about the same time the speed governor 30 takes control and holds the speed substantially constant: Even when this operating condition occurs, the pivot point B still remains under the control of the float force of float 18 and the pressure of pressure responsive device 45 and will be positioned in accordance therewith. This is possible since the pivot point B can move be positioned in accordance with the float force on float 18 and the discharge pressure, and the pulsation preventing valve mechanism will be positioned in accordance therewith.

The counterweight 48 on lever 15 is so chosen and arranged as to balance the vertical forces on pivot point B when the ma--- cally illustrated and described a pulsation preventing mechanism of'the type comprising a valve located in a by-pass .conduit connecting the discharge side of the compressor to the inlet side thereof, but it will be readily apparent that I may utilize a throttle valve located in the inlet of the compressor or a combination of a throttle valve located in the inlet of the compressor and the bypass valve located in a. conduit connecting the discharge side of the machine to atmosphere or totthe inlet thereof. In the latter case the arrangement will preferably be such that the throttle valve is first actuated, after which the by-pass valve is operated.

In accordance with the provisions of the patent statutes, I have described the principle of operation of my invention, together with the apparatus which I now consider to represent the best embodiment thereof; but I desire to have it understood that the apparatus shown is only illustrative and that the invention can be carried out by other means.

What I claim as new and desire to secure by Letters Patent of the United States. is

1. 'The combination with a compressor havinga volume governing mechanism comprising a member which is positioned in accordance with the volume being handled by the compressor, of a movable pivot for said member which is positioned in accordance with the volume being handled by the compressor and the pressure on the discharge side of the machine, a pulsation preventing valve mechanism, and means operated by the movable pivot for actuating it.

2. The combination with a compressor having a volume governing mechanism comprising a beam which is positioned in accordance with the volume being handled, of a movable pivot for the beam, means responsive to the volume being handled and to the delivery pressure for positioning said pivot, a pulsation preventing valve mechanism, and means for actuating it in accordance with the position of said movable pivot.

3. The combination with a compressorhaving a constant volume governing mechanism comprising a beam and a weight adjustable thereon, of a movable member on which the beam is pivoted, means responsive to the volume of flow for turning said beam on its pivot, suchmeans also acting to move the pivot in accordance with the volume of flow, means responsive to the pressure onthe delivery side of the compressor which acts on said member to move said pivot, a pulsation preventing valve mechanism, and means connecting it to said movable member.

4. The combination of a compressor, a motor for driving it, a regulator for the motor, a volume governing mechanism connected to said regulator, said mechanism comprising a beam having a movable pivot, means responsive to the volume of flow and to the pressure on the discharge side of the machine for positioning said pivot, a pulsation preventing valve mechanism, and means for actuating it in accordance with the position of the pivot.

5. The combination of a compressor, a governing mechanism therefor comprising a cam having a movable pivot, means responsive to the flow of fluid in the compressor for turning said beam on its pivot, said means also providing a force which tends to move the pivot, means responsive to the pressure on the delivery side of the machine for also moving said pivot, a pulsation preventing valve mechanism, and means for positioning it in accordance with the position of said pivot.

6. The combination with a compressor, of a pulsation preventing valve mechanism therefor, and means for positioning it in accordance with the ratio of volume to square root of pressure, said means comprising a beam which is actedon by a force proportional to the volume, a lever on which the beam is pivoted, means responsive to the pressure on the delivery side of the compressor which acts on said lever, and means connecting the lever to said pulsation preventing valve mechanism.

7. The combination of a compressor, a mo-" tor for driving it. a regulator for the motor, a volume governin mechanism connected to said regulator, saic mechanism comprising a beam having a movable pivot, means responsive to the volume of flow for positioning said pivot, a pulsation preventing valve mechanism, and means for actuating it in accordance with the position of the ivot.

, 8. The combination of a compressor, a motor for driving it, a regulator for the motor. a volume governing mechanism connected to said regulator, said mechanism comprising a beam having a movable-pivot, means responsive to the pressure on the discharge side of the machine for positioning said pivot, a pulsation preventing valve mechanism, and means for actuating it in accordance with the position of the pivot.

9. The combination with a centrifugal compressor, a motor for driving it, and a regulator for the motor, of a constant volume governing and pulsation preventing valve mechanism therefor, comprising a lever having a fixed pivot, a beam pivoted on the lever, means responsive to the flow of fluid in the compressor for turning the beam on its pivot, such means also acting to move the lever about its pivot, means for positioning the regulator in accordance With the angular position of the beam, means responsive to the pressure on the delivery side of the machine which acts on said lever to move it about its pivot, a pulsation preventing valve mechanism, and means connecting it to said lever.

10. The combination of a centrifugal compressor, a motor for driving it, a regula tor for the motor, a volume measuring device for controlling said regulator, a pulsation preventing valve mechanism, and means actuated by the volume governing device for positioning said pulsation preventing valve mechanism.

11. The combination with a centrifugal compressor having a motor for driving it, a regulator for the motor, a "olume governor which. normally controls said regulator, and a speed limiting device which controls it when the speed reaches a predetermined high value, of a pulsation preventing valve mechanism, and means actuated by the volume governor for positioning the-pulsation preventing valve mechanism at all times.

In witness whereof, I have hereunto set my hand this 23rd day of Jan., 1918.

CHRISTOPHER A. SCHELLENS. 

